Describe the formation of blood erythrocytes and leucocytes.
The formation of blood cells such as red and white blood cell is called haematopoiesis. All blood cells are formed in the red bone marrow and they arise from a type of cell called the hematopoietic stem cell (HSC). Within the red bone marrow, hemopoietic stem cells (haemocytoblasts) divide to produce various “blast” cells. Each of these cells mature and becomes a particular formed element. These stem cells are capable of producing and forming any of the numerous blood cell types and all components of born marrow. They are competent to maintaining their numbers by self renewal. They are also capable of giving rise to all of the formed elements of the blood. During the early stages of life, the formation of blood cells takes place in the yolk sac from where it shifts to the liver and spleen during the third month of gestation. After the seventh month, the process shifts to the bone marrow.
All blood cells develop from haemocytoblasts. Haemocytoblasts are also known as pluripotential stem cells and are found in the bone marrow. Under the influence of growths factors, these cells can replicate themselves as well as differentiate into other cells, thus providing the constant supply of blood cells.
Erythrocytes cell production
The production of erythrocytes is called erythropoiesis and occurs within the red bone marrow. Red marrow is found in the trabecular bone area this includes the ribs, vertebrae and skulls. Erythropoiesis begins with the formation of proerythroblast from hemopoietic stem cells. Over three to five days, several stages of development follow as ribosomes reproduce and haemoglobin is synthesized. Finally, the nucleus is ejected, producing the depression in the centre of the cell. Reticulo-cytes which are young erythrocytes that still contain ribosomes and endoplasmic reticulum pass through the blood stream and develop into mature erythrocytes after another day or 2. The formation of red blood cells is regulated by the balance in erythrocyte production and destruction and also by the levels of blood oxygen in the body. Erythroprotein (EPO), a hormone produced mostly by